Electroacoustic transducer

ABSTRACT

According to the present invention, there is provided an electroacoustic transducer, comprising: a first electrode; a second electrode; a piezoelectric material at least partially sandwiched between the first electrode and the second electrode; and an optical aperture extending through the electroacoustic transducer, to allow for optical communication to take place through the electroacoustic transducer.

The present invention relates generally to an electroacoustictransducer, and a power and/or data transceiver system comprising such atransducer, and a related method.

Electroacoustic transducers are often used for transmitting or receivingan acoustic signal. Such a transducer or a system comprising such atransducer may be used for example in a scanner, tomography system, ordata or power transmission.

It is of course necessary to electrically connect an electroacoustictransducer to a controller which is used for processing, or similar,signals that are transmitted or received by the transducer. If theconnection between the controller and the transducer is not given dueconsideration, then the connection itself can affect performance of thetransducer.

As already briefly discussed above, electroacoustic transducers can beused to transmit or receive data via a generated or received acousticsignal. The transfer rate of data may be satisfactorily achieved usingthe typically high frequency acoustic signals generated or received bythe transducer. However, a purely acoustic approach to data transmissionor reception might not result in sufficiently high data transfer ratesfor certain applications.

It is an example aim of the example embodiments of the present inventionto at least partially solve or avoid one or more problems ordisadvantages with prior art transducers or related systems, whetheridentified herein or elsewhere, or to at least provide a viablealternative to existing transducers or related systems.

According to a first aspect of the present invention, there is providedan electroacoustic transducer, comprising: a first electrode; a secondelectrode; a piezoelectric material at least partially sandwichedbetween the first electrode and the second electrode; and a flexibleelectrical connector in electrical connection with the first or secondelectrode at discrete points around a periphery of that electrode, thediscrete points being distributed about a substantial portion of thatperiphery.

The flexible electrical connector may have a stress relieving geometryat and/or between the discrete points.

The flexible electrical connector might generally extend around and isspaced apart from the electrode, except at the discrete points, wherethe flexible connector extends inwardly toward the electrode.

The flexible electrical connector might be shaped to have a spring-like,or planar spring-like, structure or geometry at and/or between thediscrete points.

The flexible electrical connector might comprise one or more kinematichinges.

The flexible connector might comprise a first portion that extendsaround a substantial portion of the periphery of the electrode. Theflexible connector might comprise one or more second portions that meetand extend away from the first portion and arranged to facilitate thedelivery of electrical power to/from the first portion. The firstportion might have a smaller cross-sectional area, or might be thinner,or might be narrower, further from the meeting location or locationsthan it is at or more adjacent to the meeting location or locations.

The first or second electrode might at least partially wrap around thepiezoelectric material, such that a portion of the second electrode andthe first electrode are located on a same side of the piezoelectricmaterial.

The electroacoustic transducer might further comprise an opticalaperture extending through the electroacoustic transducer, to allow foroptical communication to take place through the electroacoustictransducer.

According to a second aspect of the present invention, there is provideda power and/or data transceiver system, comprising a firstelectroacoustic transducer of the first aspect, wherein theelectroacoustic transducer is utilized as a power transmitter, a datatransmitter, a power receiver or a data receiver.

The first or second electrode of the first electroacoustic transducermight be bonded to a solid transmission medium, via which medium powerand/or data can be transmitted and/or received by the firstelectroacoustic transducer.

A second electroacoustic transducer of the first aspect might also beprovided. The first or second electrode of each of the first and secondelectroacoustic transducers might be bonded to substantially oppositeends or sides of the solid transmission medium, to allow for acousticpower and/or data transmission between the first and secondelectroacoustic transducers via the solid transmission medium.

The power and/or data transceiver system might comprise first and secondelectroacoustic controllers associated with, respectively, the first andsecond electroacoustic transducers, for: controlling the first or secondelectroacoustic transducer to generate an acoustic signal, fortransmitting power and/or data to the second or first electroacoustictransducer, via the solid transmission medium, using that signal; and/orreceiving power and/or data from the first or second electroacoustictransducer as a result of the first or second electroacoustic transducerreceiving that signal.

The power and/or data transceiver system might comprise first and secondoptical controllers associated with, respectively, the first and secondelectroacoustic transducers, for optically transmitting/receiving databetween the first and second optical controllers, thetransmission/reception being through the solid transmission medium whichis also substantially transparent to the transmission of opticalsignals, and through an or the optical aperture extending through eachof the first and second electroacoustic transducers.

The solid transmission medium might extend through a barrier, from oneside to another. The barrier might be an electrical insulator and/or beoptically opaque.

According to a third aspect of the present invention, there is provideda method of transmitting or receiving data and/or power using anelectroacoustic transducer, the method comprising generating orreceiving an acoustic signal using the transducer, in order to transmitor receive data and/or power using that acoustic signal, wherein thetransducer comprises a flexible electrical connector in electricalconnection with an electrode of the transducer, around a substantialportion of a periphery of that electrode, wherein the flexibleelectrical connector is in electrical connection with the electrode atdiscrete points around a substantial portion of the periphery of thatelectrode.

According to a fourth aspect of the present invention, there is providedan electroacoustic transducer, comprising: a first electrode; a secondelectrode; a piezoelectric material at least partially sandwichedbetween the first electrode and the second electrode; and an opticalaperture extending through the electroacoustic transducer, to allow foroptical communication to take place through the electroacoustictransducer.

Each of the first electrode, second electrode and piezoelectric materialmight extend substantially around the optical aperture.

One or more of the first electrode, second electrode and piezoelectricmaterial extend substantially around the optical aperture in asubstantially circular, annular, arc, or c-shaped manner.

The optical aperture might extend through a centre of the transducer.

The optical aperture might extend through the transducer, offset from acentre of the transducer.

The first or second electrode might at least partially wrap around thepiezoelectric material, such that a portion of the second electrode andthe first electrode are located on a same side of the piezoelectricmaterial.

The electroacoustic transducer might comprise a flexible electricalconnector in electrical connection with the first or second electrodearound a substantial portion of a periphery of that electrode. Theelectroacoustic transducer might comprise a flexible electricalconnector in electrical connection with the first or second electrode atdiscrete points around a periphery of that electrode, the discretepoints being distributed about a substantial portion of that periphery

According to a fifth aspect of the present invention, there is provideda power and/or data transceiver system, comprising a firstelectroacoustic transducer of the fourth aspect, wherein theelectroacoustic transducer is utilized as a power transmitter, a datatransmitter, a power receiver or a data receiver.

The first or second electrode of the first electroacoustic transducermight be bonded to a solid transmission medium, via which medium powerand/or data can be transmitted and/or received by the firstelectroacoustic transducer.

A second electroacoustic transducer of the first aspect might also beprovided. The first or second electrode of each of the first and secondelectroacoustic transducers might be bonded to substantially oppositeends or sides of the solid transmission medium, to allow for acousticpower and/or data transmission between the first and secondelectroacoustic transducers via the solid transmission medium.

The power and/or data transceiver system might comprise first and secondelectroacoustic controllers associated with, respectively, the first andsecond electroacoustic transducers, for: controlling the first or secondelectroacoustic transducer to generate an acoustic signal, fortransmitting power and/or data to the second or first electroacoustictransducer, via the solid transmission medium, using that signal; and/orreceiving power and/or data from the first or second electroacoustictransducer as a result of the first or second electroacoustic transducerreceiving that signal.

The power and/or data transceiver system might comprise first and secondoptical controllers associated with, respectively, the first and secondelectroacoustic transducers, for optically transmitting/receiving databetween the first and second optical controllers, thetransmission/reception being through the solid transmission medium whichis also substantially transparent to the transmission of opticalsignals, and through an or the optical aperture extending through eachof the first and second electroacoustic transducers.

The first and second optical controllers might be arranged to transmitdata using different optical wavelengths.

The solid transmission medium might extend through a barrier, from oneside to another. The barrier might be an electrical insulator and/or beoptically opaque.

According to a sixth aspect of the present invention, there is provideda method of transmitting or receiving data and/or power via anelectroacoustic transducer, the method comprising: generating orreceiving an acoustic signal using the transducer, in order to transmitor receive data and/or power using that acoustic signal, andtransmitting or receiving an optical signal through an optical apertureextending through the transducer.

It will be appreciated by the skilled person, from a reading of thedisclosure in combination with the inherent knowledge of that skilledperson, that one or more features described in relation to any oneaspect of the present invention may be combined with and/or replacedwith one or more features of other aspects of the described invention,and as such combination and/or replacement would be understood by thatskilled person to be mutually exclusive. For instances, any one or morefeatures described in relation to the transducer having a flexibleelectrical connector might be used in combination with an/or replace anyone of the features of the transducer having the concept of an opticalaperture, and so on.

For a better understanding of the invention, and to show how embodimentsof the same may be carried into effect, reference will now be made, byway of example, to the accompanying diagrammatic Figures in which:

FIG. 1 schematically depicts a power and/or data transceiver system,according to an example embodiment;

FIG. 2 schematically depicts an electroacoustic transducer, according toan example embodiment;

FIG. 3 schematically depicts further features of an electroacoustictransducer, according to an example embodiment;

FIG. 4 schematically depicts further detail of the example embodiment ofFIG. 3;

FIG. 5 schematically depicts a method of using an electroacoustictransducer, according to an example embodiment; and

FIG. 6 schematically depicts another method of using a differentelectroacoustic transducer, according to example embodiment.

Typically, an electrical connector to an electrode of an electroacoustictransducer extends towards and into contact with a single point of thatelectrode, for example in the form of a wire extending to a contactpoint or similar. This might be satisfactory in certain applications,for example in terms of the electrical connection and resultingperformance of the transducer. However, according to an exampleembodiment, a more sophisticated and more robust construction relies onthe electrical connector being flexible, and extending around asubstantial portion of a periphery of the electrode, and coming intocontact with that electrode at discrete points around that periphery. Inbrief, this might allow for better performance of the transducer, orperformance in real terms more like that expected from the transducer.

It has already been described how data transfer rates using onlyacoustic signals might be satisfactory in some applications, but notsufficient in others. An existing approach to solving this problem mightbe to use optical data transmission. However, optical data transmissionmight not be possible through some mediums or barriers. At the sametime, a degree of acoustic signal transmission might be desirable ornecessary, for a second communication channel, for redundancy, or otherpurposes, such as transmission of power across a medium or barrier. Inthe past, optical and acoustic transceiver systems have been proposed,which rely on a side-by-side optical communication system andelectroacoustic transceiver system. While this approach might solve someof the problems discussed above, such a side-by-side system results inquite an increased footprint compared with each component in isolation.An increased footprint is not desirable in many applications, where theapplications require physical penetration of an object through a barrierin order for the system to be installed. A bigger footprint might mean amore substantial hole in the barrier, which could compromise thebarrier. According to an example embodiment of the present invention,these problems may be largely overcome or avoided by providing anoptical aperture which actually extends through the electroacoustictransducer. This allows optical communication to be undertaken throughthat transducer, while allowing the transducer to perform power/datatransmission or reception in an acoustic manner. At the same time, thisapproach keeps the overall footprint of the apparatus smaller than ifthe individual components were implemented in a side-by-side manner.

These inventive principles will now be described in more detail inpractical examples, with reference to FIGS. 1 to 6.

FIG. 1 schematically depicts a barrier 2. The barrier could take one ofa large number of different forms, ranging from a wall of a building, orskin or hull of a vehicle or a ship, through to the wall of a nuclearreactor or other environment that requires separation from anotherspace. A common theme of all such barriers is that it is, in general,not desirable to make unnecessary penetrations of the barrier, forexample from one side 4 of the barrier 2 to another side 6 of thebarrier 2. This might be to prevent general damage or reduction ofstructural integrity of the barrier 2, and/or to ensure that theenvironments on one side 4 of the barrier 2 are kept quite separate fromthe environment on the second side 6 of the barrier 2. In a moreparticular example, it could well be that one side of the barrier 4contains a safe or controlled zone, whereas the other side 6 is a moreremote or uncontrolled zone. So, the control zone 4 might comprise forexample an inside of a ship or vehicle, or a control room, whereas theother side 6 might comprise an uncontrolled zone in the form of anexternal environment to the ship or vehicle, or a hazardous environmentadjacent to the control room.

Of course, in some applications it may not be necessary to compromisethe barrier 2 in any way at all, for example if purely acoustic data orpower transmission is to be undertaken across the barrier. This isbecause acoustic signals may be transmitted quite readily by the barrier2. However, in some instances, as already discussed above, acousticsignal transmission may not be sufficient for the application needs.Then, there might be a need to penetrate the barrier 2 in some way toprovide a link for optical communications, for example by one or morecables or similar. Cables or similar may, however, be difficult tosufficiently seal with respect to the barrier, and/or may not be robustenough to maintain the structural integrity of the barrier as a whole.Also, the use of cables or similar may make it very difficult, if notimpossible, to send data/power across the barrier using acousticsignals, which might be useful in certain circumstances.

In addition to the above-mentioned issues, it simply might not bepossible to ensure that the barrier 2 is transmissive with respect tooptical communications. Regardless, there might also be a need totransfer power across the barrier which might be difficult if thebarrier is not electrically conductive, and a direct wired connection isnot feasible or permitted.

It will therefore be appreciated that for one or more of the abovereasons, it is not straightforward to design and implement a power anddata transceiver system which communicates (i.e. can transmitdata/power) across a barrier.

In accordance with an example embodiment, the barrier 2 is penetrated bya specifically chosen solid transmission medium 8. In this particularexample, the solid transmission medium 8 is optically transparent to theoptical communication scheme used, but at the same time, being solid innature, can support the transmission of acoustic signals. As will bediscussed in more detail below, this means that both optical andacoustic signal transmission can occur across the barrier 2, but becausethe transmission medium 8 is solid, the barrier 2 is at least notcompromised to the extent that would be the case if one or more cableswere to extend through the barrier 2 (i.e. instead of a solid medium 8).

Typically, the solid transmission medium 8 will be unitary in form,formed from a single piece of material or even a single crystal. Fusedsilica or quartz, for example in rod form, might be a good compromise ofoptical and acoustic transmission properties and cost, but other mediumsmight be used, for instance a sapphire crystal, particularly a C-axisorientated rod, or similar.

It can be seen that the solid transmission medium 8 extends from oneside to the barrier 2 to the other side 6 of the barrier 2, as alreadydiscussed briefly above. Located at one side 4 of the barrier 2 and incontact with a first end of the transmission medium 8 is a firstelectroacoustic transducer 10. At an opposite end of the transmissionmedium 8 is located a second, similar or identical transducer 12. Eachtransducer 10, 12 may be controlled to transmit/receive acoustic signals14 via the transmission medium 8, and the signals can be used for dataand/or power transmission/reception, as is known in the art.

Importantly, each transducer 10, 12 is provided with an optical aperture16, 18. The optical aperture 16, 18 extends through the respectivetransducer 10, 12, to allow for optical communication 20, 22 to takeplace through or via the respective transducer 10, 12, and thus foroptical communication 20, 22 to take place from one side 4, 6 of thebarrier 2 to the other side 6, 4 of the barrier 2.

By locating the optical aperture 16, 18 within the footprint of thetransducer 10, 12, the overall footprint and installation complexitymight be reduced in comparison with locating an optical element adjacentto a transducer (i.e. in a side-by-side relation). In terms offootprint, only a relatively small increase in the diameter orcross-sectional size of the transducer might be needed to account forthe area ‘lost’ to the optical aperture. At the same time, locating theaperture within the transducer might avoid any excessive footprint thatmight otherwise occur due to the housings of the transducer or opticalaperture, if the aperture and transducer were located side-by-side.Installation complexity might be reduced simply by the fact that onlyone component needs to be located at the end of, and bonded to, thetransmission medium 8, as oppose to two. This might also reduce thenumber of components required, installation steps, maintenance, andreplacements etc., and so on.

FIG. 1 shows that a generally defined first part 24 of an overall powerand/or data transceiver system might be located on the first side 4 ofthe barrier 2. That first side 4 might be a more controlled environmentwhere power 26 might be readily supplied to, and/or generated by, thatfirst part 24 of the system. A second part 28 of the overall system islocated on the second or other 6 side of the barrier 2, which might belocated in an environment where the supply of power is not practical oreven possible.

The first part 24 of the system comprises a first electroacoustictransducer controller 30 for controlling the signal 32 applied to thefirst transducer 10. First controller 30 will control the signal 32applied to the transducer 10 to then transmit an acoustic signal 20across the barrier 2, via the medium 8, to the second transducer 12. Thesignal might form or comprise data. However, such data transmissionmight not be desirable or required, since there is already the facilityto provide optical communication, as will be discussed in more detailbelow. Thus, the controller 30 might control 32 the transducer 10 totransmit an acoustic signal 14 via the transmission medium 8, which isreceived by the transducer 12 and used to generate power on the secondside 6 of the barrier 2. Thus, power might be transmitted across thebarrier 2, without the use of a direct electrical connection across thatbarrier 2. The power might be used to power one or more components ofthe second part 28 of the overall system, as discussed in more detailbelow.

The first part 24 of the system also comprises a first opticalcontroller 34, for optically communicating 20, 22 through the barrier.The first optical controller 34 might comprise an optical source 36,which might comprise, or be in connection with a data source similar.The optical source 36 might be chosen for the specific application, andmore particularly for the desired data transfer 20 rate of thatapplication. For instance, the optical source 36 might comprise one ormore LEDs, which could support data transmission of up to around 300Mbps. In more data intensive applications, the optical source 36 mightcomprise one or more laser diodes or lasers. A laser diode controlledusing current modulation could support data transfer rates up to 1 Gbps.With the combination of a well-defined polarised laser or laser diodeand a modulator external to the laser cavity, data transfer rates in theregion of tens of Gbps could be supported.

The optical controller 34 also comprises an optical receiver 38 forreceiving 22 optical signals at the first side 4 the barrier 2. Theoptical receiver 38 will, of course, be sensitive to the reception ofoptical signals transmitted from the other side 6 of the barrier. Itmight be convenient to ensure that data transmitted in one direction isundertaking using optical communications at a certain opticalwavelength/frequency, and optical communication in the other directionis undertaken using a different wavelength/frequency, purely for ease ofsignal processing/differentiation. Alternatively, orthogonal opticalpolarisations for each optical signal 22, 24 could be used inconjunction with polarisation filtering.

The optical controller 34 might additionally comprise a beam splitter40, or other optical modulator or manipulator which allows fortransmitted and received optical signals to be handled and processed ina convenient manner, through/via the single aperture 16 in thetransducer 10. For instance, in FIG. 1, it is shown that the transmittedoptical signal 20 generally passes through the beam splitter 40, whereasthe received optical signal 22 is generally reflected by that beamsplitter 40. Again, the use of different transmission/receptionwavelengths/frequencies, or alternatively orthogonal opticalpolarisations, might assist in this optical handling, by the opticalmanipulator or modulator 40 being able to selectively transmit/reflectoptical signals of certain wavelength/frequencies, or alternativelyorthogonal optical polarisations.

The transmission of power across the barrier 2 via medium 8 using anacoustic signal may take place in advance of, at the same time as, orpossibly even after the transmission of data in an optical manner.Although the second part 28 of the overall system on the second side 6of the barrier 2 might not be provided with power by any other meansthan the reception of an acoustic signal from the first transducer 10,the second part 28 might nevertheless (in some embodiments) have atemporary power store in the form of a battery or capacitor that mightbe able to receive and store power derived from a received acousticsignal 14. This amount of power might not be significant, but mightnevertheless allow operation of one or more components of the secondpart 28 of the system without the part 28 receiving power from firsttransducer 10 at that precise moment in time.

A typical example operation of the system of FIG. 1 will now bedescribed.

The first electroacoustic controller 30 will generate a signal 32, forexample a high frequency signal 32, for driving of the transducer 10. Inthis example, the signal 32 will not comprise any meaningful data, butwill simply be used to drive the transducer 10 in order to transmit anacoustic signal 14 through medium 8 to the second transducer 12, so thatpower can be derived via the second transducer. The second transducer 12receives the acoustic signal 14 and converts the acoustic signal 14 intoan electrical signal 42, which is passed onto a (second) controller 44of the second acoustic transducer 12.

Power derived from reception and processing of the acoustic signal 14may be used to drive 46 for instance, a second optical controller 48 ofthe second part 28 of the overall system. Although not shown, thecontroller 44 may be used to supply power to a sensor, actuator, or someother component located on the second side 6 of the barrier 2, and/orthe second optical controller 48 which itself may be or comprise such asensor, actuator, or other component.

The second optical controller 48 may comprise the same sort of opticalsource 50 and receiver 52 as already shown in and described withreference to the first part 24 of the system, located on the first side4 the barrier 2. Of course, and as already described, thetransmission/reception might operate at a different opticalwavelength/frequency or alternatively orthogonal optical polarisation.Again, a beam splitter 54 or other like optical modulator 54 may also beincorporated within the optical controller 48, for the same reasons asalready described above with the optical modulator 40 of the first part24 of the system.

Data in optical form may be conveniently transmitted between thedifferent sides 4, 6 of the barrier 2 via appropriate control of thetransmitters 36, 50 and receivers 38, 52 of the different parts 24, 28of the system located, respectively, on different sides 4, 6 of thebarrier 2.

As might be expected, the data can take any convenient form as necessaryto fulfil the requirements of the application in question. For instance,data may be transmitted from the first part 24 of the system to thesecond part 28 of the system in order to control, or for use by, asensor or actuator or other component on that second side 28 of thesystem. Data may be transmitted in the other direction for the same orsimilar reasons or, alternatively and/or additionally, data might berepresentative or include information from sensors located on the secondside 6 of the barrier 2.

The data transmitted between the different parts 24, 28 of the systemmight not necessarily relate to sensing, or actuating components or thelike, of or associated with those parts 24, 28. For instance, the datathat is transferred may be used to monitor power outputs or inputs withrespect to the different transducers, sources, receiver, and relatedcontrollers, or data or power transmission. The data might be useful foroptimising or monitoring the performance of the system as a whole. Forinstance, the data might be used to ensure that the acoustic signal thatis used to power the second part 28 of the system is efficientlytransmitted and/or received to maximise power transfer or again, byappropriate impedance matching or fine tuning of acoustic transmissionproperties, for example central frequency, amplitude and so on.

In a more specific example of optimisation using feedback, since theends of the solid transmission medium 8 are parallel, acoustictransmission of power between the transducers 10 and 12 will becharacterised by rapid variations of transmitted power with frequencydue to acoustic interference effects. Information on the acoustic powerdelivered into second controller 44 could be feed back to the firstcontroller 30 via data carried by the optical communication beam 22, andused as the basis of a feedback loop to optimise power delivery at thesecond controller 44.

FIG. 1 has shown the transmission of power 14 across the barrier 2 inone direction and the bi-directional optical transmission/reception 20,22 of data across the barrier 2. The power is transmitted acoustically14. There may be little or no need to transmit meaningful data acrossthe barrier using an acoustic signal due to the presence of the opticalcommunications link. However, uni-directional or bi-directionaltransmittal/reception of data in an acoustic manner can also beimplemented using the arrangement of FIG. 1. Data could be transmittedas part of a transmission of power, in-between periods where power istransmitted, or instead of power transmission. Again, the use of a solidtransmission medium that supports acoustic signal propagation allows forthis example to be realised, if and when necessary. For instance, theacoustic transmission might be used as redundancy, for instance if theoptical transmission fails permanently or temporarily. A slower datarate might be better than no data transfer at all.

As would be understood from the description of FIG. 1, the system allowsfor a part of a system located on one side or barrier to be powered by apart of a system on another opposite side of the barrier, in combinationwith high data transfer rates to take place. All of this is achievedwithout any, or at least significant compromise of the key properties(be they either electrical or mechanical, etc.) of the barrier 2 itself.

It will be noted that the detailed description of thetransmission/reception of optical/acoustic signals has been omitted,since the invention does not relate to such application specific detail,but instead to the provision of an aperture in the transducer, andflexible connections as discussed below. The skilled person in the fieldwill, with a reading of this disclosure, be able to implementoptical/acoustic transmission/reception, from their own inherentknowledge in that field, and of neighbouring fields to which theinvention might relate.

Similarly, controllers have been described quite generally, since theirconstructions are not pivotal to the understanding invention. Inpractical example, a controller could comprise more components, forexample amplifiers, rectifiers, diodes, power monitors, etc., as wouldbe understood by the skilled person.

FIG. 2 schematically depicts a cross-sectional view of the firsttransducer 10, and a part of the solid transmission medium 8 to whichthe transducer 10 is attached. Although not shown, the same principlesthat will be described will apply equally to the second transducerlocated at an opposite end of the solid transmission medium 8.

The transducer 10 comprises a piezoelectric material 60, which extendsaround the optical aperture 16. The piezoelectric material or layer 60is substantially sandwiched between a first electrode 62 and a secondelectrode 64.

At least a part of the second electrode 64 partially wraps around thepiezoelectric material 60 such that a portion of the second electrode 64and the first electrode 62 are located at the same side of thepiezoelectric material 60 and substantially in the same plane. Thismight allow for easier electrical connection for one or both of theelectrodes 62, 64, for example to the controller described above.Without such wrapping around, it might be difficult to make goodelectrical connection to the second electrode 64, due to the need tobond that electrode to the medium 8, particularly if a non-electricalconducting bonding material is used between medium 8 and secondelectrode 64.

The first and second electrodes 62, 64 are electrically separated fromone another by way of one or more isolator or insulator elements 66,which could be formed from an independent component, or an extension ofthe piezoelectric material 60 that is non/un-metallised.

The first transducer 10 is bonded to an end of the transmission medium 8by bonding the second electrode 64 to the end of that medium 8. Beforesuch bonding, the transmission medium 8 might be appropriately cleanedand polished. This might assist not only in the bonding process, butalso in terms of the acoustic and/or optical coupling of signals intothat medium 8 from or via the transducer 10.

The bond might comprise any suitable adhesive or bonding agent orsimilar 68. Spacers 70 might also be included, to maintain a consistentand/or desired spacing between the medium 8 and the transducer 10, againto optimise coupling of signals into the medium 8. Spacers might alsoprevent contamination in the bond/bonding process from non-uniformlypositioning or loading the transducer 10, or the presence of smallerdiameter foreign bodies that might otherwise result in a non-uniformbond thickness. Spacers 70 might take the form of rods, spheres, orsimilar.

The electrode or part thereof 64 which is bonded to the medium 8 issubstantially planar in form, so as to assist in uniform bonding of thetransducer 10 onto the medium 8, and thus uniform positioning/loading ofthe transducer 10. The opposing side of the transducer 10, whichincludes, substantially, the first electrode 62 and a part of the secondelectrode 64 will also, together, be planar in form. This ensures thatloading pressure by a tool or similar might be more easily and uniformlyapplied to surfaces of those electrodes/parts 62, 64 to accurately andsecurely bond the transducer 10 to the medium 8 with a uniform bondthickness. Typically this tool will include a thin resilient pad on thesurface to be placed directly against the transducer 10 or a surfacethereof. This resilient pad is intended to deform around any high pointson the transducer or any small diameter particles on the surface of thetransducer. At the same time, this also helps ensure that uniformloading of the electrodes 62, 64, piezoelectric material 60 andtransducer 10 in general, takes place, to ensure that final performanceof the transducer 10 is not adversely affected by the bonding due to anuncontrolled bond layer thickness across its bonded surface.

The optical aperture 16 is shown. The optical aperture 16 extendsthrough the first electrode 62, piezoelectric material 60 and secondelectrode 64. This might alternatively/or traditionally be described ordefined as the one or more of the first electrode 62, piezoelectricmaterial 60, and second electrode 64, as appropriate, extending aroundthat optical aperture 16, in example in a circular-like or morespecifically annular, c-shape, or arc-like manner. The diameter of thisoptical aperture will typically be smaller than the diameter of the holein the piezoelectric layer 60 due to the formation of a fillet of thebond layer material that will build up on the side wall in the holethrough the piezoelectric layer 60.

The optical aperture 16 could comprise one or more of: a space or gap;an optical element such as a lens; or a solid piece of opticallytransparent material such as fused silica or quartz. The choice mightdepend on the optical communications system that is implemented.

The optical aperture 16 is shown as being circular in cross-section.However, the aperture could be rectangular or square. Stress relievingfillets might be provided in more angular apertures, for examplerectangular or square apertures.

In all Figures shown and described herein, the optical aperture 16 isshown as being located substantially at the centre of the respectivetransducer. In some examples, this might be advantageous, in terms ofthe overall manufacture and packaging of the transducer, but also interms of aligning the optical aperture with respect to another acrossthe barrier via the medium 8. However, locating the optical apertureoff-centre might also have benefits. This is because there will be animpact on the transmission of the acoustic signal by the very presenceof the optical aperture. So, locating the optical aperture off-centremight yield a superior reduction of acoustic energy being coupled intohigher diffraction orders of the Airy circle diffraction side lobes;compared to the increase in the acoustic energy coupled into the higherdiffraction orders when a circular obstruction is placed in front of anotherwise uniformly emitting circular aperture. That is, in other words,locating the optical aperture 16 off-centre might lead to a better ormore efficient transmission of acoustic power across the barrier, andtherefore a more efficient delivery of power to the system parts on theother side of the barrier.

Now that the transducer 10 has been described in more detail, anotherspecific example of optimisation of the overall system using feedbackacross the barrier can be provided. Piezoelectric transducers made usingLead Zirconium Titanate (PZT) in particular have a relative dielectricconstant that is a strong function of the environmental temperature thatin turn affects the ‘dead’ capacitance of/across the piezoelectric layer60 of the transducer 10. The dead capacitance of the transducer 10 isthe capacitance of the transducer's electrodes at the operatingfrequency, in the absence of any piezoelectric induced modifications tothe effective reactance of the transducer 10. As a consequence, theoptimal operating frequency for the acoustic power transmission linkwill be a function of temperature, and so as part of any control loopfor the exact operating frequency, the temperature of the twotransducers in the system could be monitored so that the optimalfrequency of operation is selected for the two not necessarily identicaltemperature transducers. Consequently as part of the electrical feedbackloop regarding control of the operating frequency of the power link, thetemperature of the remote transducer should be fed back (e.g. via theoptical part of the system) to allow the optimal selection of a roughstart frequency drawn from a look up table (in practice this mightactually be a second start frequency, since no data on temperature cancome back until some power is sent to the remote/other end/side). Theoperating frequency is then optimised to yield a maximum in the vicinityof the rough start second frequency using a feedback loop to sit thefrequency on a local peak for signal transmission.

FIG. 3 is a plan view of the transducer 10 and transmission medium 8 ofFIG. 2, but also showing additional details and items in the form ofelectrical connections to/from the transducer 10.

In order to apply a potential difference across the piezoelectric layer60, it is of course necessary to supply the transducer 10 withelectrical power. Conversely, there may be a need to extract anelectrical signal from the transducer 10. Electrical connectors will berequired to facilitate such connection. In an example embodiment, atleast one of those electrical connectors is flexible in nature. Moreparticularly, the flexible connector might have an even more specificadvantageous configuration.

Referring back to FIG. 3, a flexible electrical connector 80 is shown.The flexible electrical connector 80 extends around a major portion ofthe periphery of the second electrode 64 to which the connector 80 isattached/electrically connected. The flexible connector 80 is attachedand electrically connected to the second electrode 64 at discrete points82 about the periphery of the second electrode 64. The discrete points82 might take the form of a solder or other electrically connectingattachment or bond. The discrete points 82 are distributed about asubstantial portion of the periphery.

The transducer 10 might work quite well if only a single point ofelectrical contact was made to the, for instance, the second electrode64. However, distributing the electrical contacts 82 might provide amore distributed electrical contact to the electrode 64. Thisdistributed electrical contact will reduce the sheet current density,especially when the electrode 64 is a thin metallisation layer orsimilar, typical of transducers. Reducing sheet current density mightimprove the overall electrical and physical operation of the transducerin terms of more uniform electrical driving and power extraction, andallow higher power operation prior to the onset of fusing of themetallisation layer due to excessive current densities.

The distributed nature of both the electrical and physical contacts 82with the electrode 64 might also have physical benefits, for example byallowing a larger area of the transducer to be uniformly loaded duringbonding with bonding tool, rather than being constrained by the presenceof a simple ring shaped electrical interconnect to the second electrode64 to loading just the first electrode 62. Another physical benefit isthat flexible connections 80 between adjacent contacts 82 will reducethe impact of coefficient of thermal expansion mismatch between theinterconnect material used in the construction of items 112, 80 and thelateral coefficient of thermal expansion of the piezoelectric layer 60.The flexible connections 80 in particular will reduce any compressivestress applied close to the outside perimeter of the transducer 60resulting in physical bowing of the transducer from its ideal flatprofile prior to bonding.

Any force or weight or the like that might result due to the presence ofthe connector 80 or the interaction between the connector 80 and theelectrode 64/piezoelectric layer 60 by way of contacts 82 might also bemore uniformly and evenly distributed.

Indeed, it can be seen that the flexible electrical connector 80 isprovided with stress relieving geometry 84 at and/or between the contactpoints 82. The aim of this is to prevent stress build up at theconnector 80 which might otherwise be imparted onto or into theelectrode 64/piezoelectric layer 60, or to simply absorb within theconnector 80 some of the forces that might otherwise be imparted ontothe electrode 64/piezoelectric layer 60.

The stress relieving geometry, or a geometry that at least assists in amore uniform distribution of loads or the like on the electrode64/piezoelectric layer 60, might be achieved in one of a number of ways.For instance, the flexible electrical connector 80 generally extendsaround and is spaced apart from the electrode 62, but at the discretepoints 82 the flexible connector 80 extends inwardly and into contact 82with the electrode 64. This inwardly projecting or extending geometry orshaping might assist in the stress relief and the more uniformdistribution of force, for example acting in a spring-like manner orsimilar.

The Figure shows a quite angled geometry of the connector 80, but thisgeometry could be more curved or rounded to reduce points of stress ofloading.

A flexible connector 86 might also be used to electrically connect thefirst electrode 62 to other components, for example the controllerreferred to above. The flexible connector 86 might have at least some ofthe benefits of the connector 80. This flexible connector 86 might beallowed to flex in some way, for example by being slightly slack,bendable or bent, flexible, or generally non-straight, so as to allowfor some movement between the transducer 10/first electrode 62 andcomponents connected thereto (e.g. a controller).

FIG. 4 shows another geometry that could be used in combination with, orin place of the geometry of the flexible electrical connector of FIG. 3.In FIG. 4, a different flexible electrical connector 90 is shown. Thepurpose and function of the electrical connector 90 might be much thesame as that described in relation to FIG. 3. The geometry andproperties exhibited by this particular flexible electrical connector 90is (more) spring-like and more particularly planar spring-like. Theplane of the spring is in parallel to the plane of theelectrodes/piezoelectric layers of the transducer. This means thatrelative movement or expansion etc., between different parts of theflexible connector 90, or between the connector 90 and the electrode towhich it is attached, or the electrode, can more readily and repeatedlybe accommodated, as will be discussed in more detail below. Theinclusion of kinematic hinges 92 (which might be described as joints orcouplings), in the form of cut-outs or recesses, at or adjacent topoints where moving or flexing might take place also assistsmechanically isolating the electrode/piezoelectric layer from (external)stress.

The spring geometry might take any one of a number of different forms,but the planar spring geometry might be advantageous in accounting forexpected expansion or relative movement in-plane. The planar spring-likegeometry might comprise of a diamond or rhombus or quadrilateral orparallelogram frame-structure 94. Two corners of such an arrangement maybe in connection with the parts of the connector 90 that are in contact82 with the electrode. Other corners or vertices of the structure 94might be readily free to move, subject to constraint by an optionallinking bar, or strut, or arm 96. The overall force or spring-likeproperties of the structure 94, 96 will be determined by the materialused for the overall construction, and the dimensions involved and also,most importantly, by the cross sectional thickness of the linking arm96. This linking arm 96 might be particularly configured to ensure thespring has a particular stiffness.

The presence of the flexible connector described above is advantageousin, for example, minimising the stress on the electrodes to which theconnector is attached, and therefore the piezoelectric layer. Stress maybe imposed due to differential forces acting on one or both of theconnector or the electrode, for example as a result of differentialheating of the connector and the electrode/piezoelectric layer, ordifferent coefficients of thermal expansion of the connector and theelectrode. Additionally and/or alternatively, the isolation between theconnector and the electrode/piezoelectric layer (i.e. general transducerstructure) might have more general benefits in terms of mechanicallyisolating the electrode/piezoelectric from the connector and to whateverthe connector is attached, which might improve transducer performance orsignal generation or reception. Also or alternatively, improvementsmight relate to reducing stresses on the metallic films of thetransducer structure. For example if the interconnect is not flexibleand it heats up due to current flow, then this will stress the surfacejoint of the metallic films adhering to the piezoelectric layer, andpotentially cause it to lose key and peel off. As well as mechanicallyisolating the electrode/piezoelectric from the connector, theconstruction might also assist in the fabrication of thetransducer/system as a whole. For example, the spring-like geometry orfunctionality might prevent the contacts 82 from flopping about duringthe construction process, making it easier to attach these to theelectrode in a quick and efficient manner.

The arrows in FIG. 4 depict in more detail an example of thefunctionality described above. Arrow 100 schematically depicts aseparation between adjacent contacts 82. The piezoelectric layer of thetransducer typically has a lower coefficient of thermal expansion thanthe flexible electrical connector 90. Heat generated duringsoldering/heat induced application/bonding of the contacts 92 will causedifferential expansion of the piezoelectric layer and flexible connector90, which could cause the piezoelectric layer to bow. However, thespring-like geometry and construction 94, 96 serves to avoid or at leastpartially reduce the bowing.

FIG. 4 shows that as the separation 100 reduces, there is differentialcontraction of the flexible connector 90 as indicated by arrows 102.However, as opposed to this causing a build up of significant stress inthe connector 90, which might have an adverse effect on the overalltransducer performance/structural integrity/configuration, the arrows104 show that spring-like structure 94, 96 can flex in response to thecontraction 102 to relieve the stress. Linking arm 92 provides thebiasing or return force 105.

Mainly physical, structural benefits of the flexible electricalconnector have been described above. However, physical properties of theflexible connector might be different around its circumference, as thatcircumference extends around the electrode, to affect electricalproperties. For instance, referring back to FIG. 3, the flexibleconnector 80 might comprise a first portion 110 that extends around asubstantial portion of the periphery of the second electrode 64, and oneor more second portions 112 that extend away from the first portion 110and which are generally arranged to take the delivery of electricalpower to/from this portion 110. The first portion 110 might have asmaller cross-sectional area, or is thinner, or is narrower, furtherfrom where the second portions 112 meet the first portion 110 than at,or more adjacent to, the meeting locations. The amount of current thatreaches the portion 110 further away from portions 112 receives lesscurrent. So, making the cross-sectional area or similar smaller at theselocations might help ensure a more consistent and uniformed delivery ofcurrent about and around the electrode, thus improving the uniformdriving of the transducer 10 as a whole.

The flexible connectors might be formed entirely from conductivematerial, or from conductive material located on, embedding, or embeddedwithin, a flexible carrier, for example a flexible polymer/plasticcarrier.

The use of a flexible connector as described above might be advantageousin combined use with the optical aperture. For example, preventingbowing of the transducer or piezoelectric layer therefor might preventchanges to the shape of the optical aperture. This might improve opticalperformance. There are also potential issues with adhesive or other bondmaterial squeezing out into the optical aperture, as a result of thebowing, and thus blocking the aperture. So, limiting or preventing suchbowing can limit or prevent such blocking. Adhesive or other bondmaterial might be applied as small controlled dots, away from theoptical aperture, to also limit or prevent such blocking. Capillaryaction will transport the adhesive/bond material over the entire surfacethat needs to be bonded, for example to transmission medium.

In an alternative and/or additional approach to addressing the potentialrisk of the adhesive/bond material leaking over/into the opticalaperture on the end of the solid transmission medium, a small diameterdisc (or shape matching the aperture) of matching optical material (e.g.at least index matched) close or identical to the transmission mediumcould be bonded to the end of the solid transmission medium, for exampleusing an optical adhesive that is also index matched to the medium. Thiswould remove the risk of adhesive/bond material obscuring the opticalaperture. A pre-bonded optical disc would also allow the transducer tobe gently moved slightly back and forth during the bonding process, tohelp the adhesive layer ooze out until it bottoms off onto the spacers(e.g. micro-pearl rods or spheres) used to control the thickness of thetransducer bond. Pre-bonded discs could be used to conveniently co-alignthe two transducers more accurately, which might help in terms of bothoptical and acoustic transmission/reception.

In an operating environment subject to high levels of shock orvibration, it is likely to be important that the rod of the solidtransmission medium is robustly restrained within the hole in thebarrier into which the transmission medium is inserted. This can beachieved with locking clamps fixed onto the barrier at each side of thebarrier, to prevent longitudinal movement of the rod of the solidtransmission medium. Coupling of acoustic power into the clamps applieddirectly onto the surface of piezoelectric transducer can be largelysuppressed by using, for example, an engineering plastic the acousticimpedance of which is very much lower than that of the transducer.Rotational movement of the overall assembly under vibration can beprevented by non-electrically conductive pins that insert into/throughmatching apertures in the piezoelectric layer. A high level ofrotational symmetry (in terms of mass) of the overall assembly meansthat turning forces on the assembly will be small.

The principles and methodologies have been described in relation toFIGS. 1 to 4 in quite a specific manner. FIGS. 5 and 6 depict moregenerally methodology that relates to the transducer structure andoperating principles described above. For instance, FIG. 5 is aflowchart showing use of the transducer described above having aflexible electrical connector 120. The use comprises generating orreceiving an acoustic signal using the transducer, in order to transmitor receive data and/or power using that acoustic signal 122. FIG. 6 is aflowchart which schematically depicts a method that might be related toor used in isolation of the method of FIG. 5. The method comprisesgenerating or receiving an acoustic signal using a transducer, in orderto transmit or receive data and/or power using acoustic signal 130. Themethod further comprises transmitting or receiving an optical signalthrough an optical aperture extending through the transducer 132. Asalready discussed above, the acoustic and optical signals might begenerated or transmitted or received in any particular order, forexample the acoustic signal being generated in advance of the opticalsignal, at the same time as the optical signal, or after the opticalsignal.

Components located on one side of a barrier might be described as beingassociated with one another, in terms of giving those components acollective locational label, for example in comparison with componentsassociated with an opposite side of the barrier.

The electroacoustic transducers described above have, in general, beendescribed as part of power and/or data transceiver system. However, itwill of course be apparent that the described electroacoustictransducers exhibit many of the described advantages in isolation, orindependently of, this system as a whole. That is, the describedelectroacoustic transducers might be used in isolation in certainembodiments, or in combination with like transducers, or evenretrofitted into systems comprising similar transducers to improve theperformance of such systems as a whole.

Although a few preferred embodiments have been shown and described, itwill be appreciated by those skilled in the art that various changes andmodifications might be made without departing from the scope of theinvention, as defined in the appended claims.

Attention is directed to all papers and documents which are filedconcurrently with or previous to this specification in connection withthis application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings) may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise.

Thus, unless expressly stated otherwise, each feature disclosed is oneexample only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

1. An electroacoustic transducer, comprising: a first electrode; asecond electrode; a piezoelectric material at least partially sandwichedbetween the first electrode and the second electrode; and an opticalaperture extending through the electroacoustic transducer, to allow foroptical communication to take place through the electroacoustictransducer.
 2. The electroacoustic transducer of claim 1, wherein eachof the first electrode, second electrode and piezoelectric materialextend substantially around the optical aperture.
 3. The electroacoustictransducer of claim 2, wherein one or more of the first electrode,second electrode and piezoelectric material extend substantially aroundthe optical aperture in a substantially circular, annular, arc, orc-shaped manner.
 4. The electroacoustic transducer of claim 1, whereinthe optical aperture extends through a centre of the transducer.
 5. Theelectroacoustic transducer of claim 1, wherein the optical apertureextends through the transducer, offset from a centre of the transducer.6. The electroacoustic transducer of claim 1, wherein the first orsecond electrode at least partially wraps around the piezoelectricmaterial, such that a portion of the second electrode and the firstelectrode are located on a same side of the piezoelectric material. 7.The electroacoustic transducer of claim 1, further comprising a flexibleelectrical connector in electrical connection with the first or secondelectrode around a substantial portion of a periphery of that electrode.8. A system comprising the electroacoustic transducer of claim 1,wherein the electroacoustic transducer is utilized as a powertransmitter, a data transmitter, a power receiver, or a data receiver.9. The system of claim 8, wherein the first or second electrode of thefirst electroacoustic transducer is bonded to a solid transmissionmedium, via which medium power and/or data can be transmitted and/orreceived by the first electroacoustic transducer.
 10. The system ofclaim 9, wherein the electroacoustic transducer is a firstelectroacoustic transducer, the system further comprising a secondelectroacoustic transducer, the first or second electrode of each of thefirst and second electroacoustic transducers being bonded tosubstantially opposite ends or sides of the solid transmission medium,to allow for acoustic power and/or data transmission between the firstand second electroacoustic transducers via the solid transmissionmedium.
 11. The system of claim 10, comprising first and secondelectroacoustic controllers associated with, respectively, the first andsecond electroacoustic transducers, for: controlling the first or secondelectroacoustic transducer to generate an acoustic signal, fortransmitting power and/or data to the second or first electroacoustictransducer, via the solid transmission medium, using that signal; and/orreceiving power and/or data from the first or second electroacoustictransducer as a result of the first or second electroacoustic transducerreceiving that signal.
 12. The system of claim 10, comprising first andsecond optical controllers associated with, respectively, the first andsecond electroacoustic transducers, for optically transmitting databetween the first and second optical controllers, the transmission beingthrough the solid transmission medium which is also substantiallytransparent to the transmission of optical signals, and through theoptical aperture extending through each of the first and secondelectroacoustic transducers.
 13. The system of claim 12, wherein thefirst and second optical controllers are arranged to transmit data usingdifferent optical wavelengths.
 14. The system of claim 9, wherein thesolid transmission medium extends through a barrier, from one side toanother, and wherein the barrier is an electrical insulator and/or isoptically opaque.
 15. A method of transmitting or receiving data and/orpower via an electroacoustic transducer, the method comprising:generating or receiving an acoustic signal using the transducer, inorder to transmit or receive data and/or power using that acousticsignal; and transmitting or receiving an optical signal through anoptical aperture extending through the transducer.
 16. The method ofclaim 15, wherein the optical aperture extends through a centre of thetransducer.
 17. The method of claim 15, wherein the optical apertureextends through the transducer, offset from a centre of the transducer.18. The method of claim 15, wherein the electroacoustic transducer is afirst electroacoustic transducer, the method further comprising:controlling the first electroacoustic transducer to generate theacoustic signal, for transmitting power and/or data to a secondelectroacoustic transducer, via a solid transmission medium, using thatacoustic signal; and/or receiving power and/or data from the secondelectroacoustic transducer as a result of the second electroacoustictransducer receiving that acoustic signal.
 19. The system of claim 8wherein the system is a power system.
 20. The system of claim 8 whereinthe system is a data communication system.